Device for coating objects with pulverized or granular particles or flakes or fibres

ABSTRACT

An arrangement for coating objects by depositing small metal particles on a collecting element includes an insulating support for the particles, a first electrode on one side of the support, a counter-electrode on the other side of the support having spaces therethrough, and an arrangement for creating a first alternating current electrostatic field between the counterelectrode for moving the particles off of the support and a second arrangement for creating an electric field between the collecting element and the electrode on the opposite side of the counter-electrode from the support to cause the particles to move to the collecting element, the counter-electrode and the collecting element being charged with different potentials.

United States Patent 11 1 Stutz et a1.

[ DEVICE FOR COATING OBJECTS WITH PULVERIZED OR GRANULAR PARTICLES ORFLAKES OR FIBRES [76] Inventors: Erwin Stutz, Wetzgauerstrasse.

Mutlangen; Hugo Brennenstuhl, Seestr. 1-3, Tiibingen-Pfrondorf, both ofGermany 22 Flledi July 24,1972

21 Appl. No.: 274,614

[52] US. Cl. 118/621; 117/17; 118/627;

118/629; 1l8/DIG. 5 [51] Int. Cl. B05c 5/02 [58] Field of Search 117/17,93.4 R, 93.4 NC;

ll8/D1G. 5,621, 627, 629, 637

1 June 10, 1975 Primary Examiner-Mervin Stein Assistant Examinerl.eoMillstein [57] ABSTRACT An arrangement for coating objects by depositingsmall metal particles on a collecting element includes an insulatingsupport for the particles, at first electrode on one side of thesupport, a counter-electrode on the other side of the support havingspaces therethrough. and an arrangement for creating a first alternatingcurrent electrostatic field between the counter-electrode for moving theparticles off of the support and a second arrangement for creating anelectric field between the collecting element and the electrode on theopposite side of the counter-electrode from the support to cause theparticles to move to the collecting element, the counter-electrode andthe collecting element 10 Claims, 9 Drawing Figures [561 ReferencesCited UNITED STATES PATENTS 2,684,656 7/1954 Ransburg 118/51 3,248,2534/1966 Barford C131 118/627 1 3.337.908 8/1967 NCISOfl, Jr. et a1...18/4 bemg charged d'fferem pmemals' 3,537,426 11/1970 Spiller 118/629PATENTEBJUMO I975 3 8 207 orlitvlsa aul 1 DEVICE FOR COATING OBJECTSWITH PULVERIZED ()R GRANULAR PARTICLES OR FLAKES OR FIBRES The presentinvention relates to an apparatus for coating objects with pulverized orgranular particles or flakes or fibres, in which the particles used forcoating are sprayed or hurled by means of an electrostatic field on acollecting element which is the object to be coated. The invention alsorelates to a device for performing this method.

The process according to the invention is characterized in that thecoating material is brought in a fine dispersion uppon a supportpreferably of insulating material, on the side thereof facing thecollecting element so that it is spread in an even or almost even layerloosely on the latter further that the coating material lying on thesupport is shaken free of the support, e.g. by electrical means,preferably by means of an alternating field, or by mechanical means suchthat it becomes immersed into an electrostatic field between the supportand the collecting element, further that the loosened particles ofcoating material are accelerated by the electrostatic field until theyreach the collecting element, and further that the particles of coatingmaterial hurled off the support are made to adhere to the collectingelement by allotting or associating to the latter a potential whichdiffers from the potential of one of the electrodes of the electrostaticfield, after which the coating material may be intimately bonded withthe collecting element by baking or by means of adhesive.

The new device is distinguished by the fact that perfect coating of thedesired collecting element may now be achieved in the most simplemanner, e.g. even in mass production and that an adequate intensity forany number of applications of the new method is obtained, and, moreover,the adhesion of the particles to the collecting element may be achievedin the most simple manner. Above all, however, with the device accordingto the invention, a layer of even thickness on the collecting elementmay be obtained because only charged particles are shot out," with theconsequence that these particles are orientated to one another anddispersed evenly over the surface.

A further advantage of the device according to the invention consists inthat expenditure on apparatus is low, thus, e.g. change of colour of thecoating material may be carried out faster and more easily and noconventional recovery system is necessary. A device according to theinvention to execute the new method is characterized in that on the sideof the insulating support facing away from the collecting element anelectrode is provided and between the insulating material and thecollecting element there is at least one counter electrode which may bein the form of a lattice or grid or may consist of single wires and maypossibly be insulated, and that either the collecting element itself isan electrode or an electrode is placed before or behind it.

In the drawings there are shown several examples and embodiments of theinvention. There show:

FIGS. I and 2 two different embodiments of the new device for performingthe method according to the invention diagrammatically and in side view,

FIG. 3 a detail of further modification of the invention again indiagrammatical representation,

FIGS. 4, 5 and 6 various embodiments of the device according to theinvention in a merely schematical representation in side view and FIGS.7, 8 and 9 further modifications of the invention in a cross sectionalside view and in detail.

The first embodiment of the device according to the invention shown inFIG. 1 comprises as its most important features an insulating support 1,which, e.g. may be a plate, a hollow body of synthetic material, or maybe in the form of a tape or of a conveyor belt, or which, e.g., incertain applications may be a sieve or plate of permeable material, e.g.synthetic foam or ceramic, a collecting element 2 which is the body orsupport to be coated and faces the insulating support 1 and electrode 3on the side of the insulating support 1 facing away from the collectingelement 2, a counter electrode 4 between the insulating support and thecollecting element, and a further electrode 5 on the side of thecollecting element facing away from the insulating support. Theelectrodes 3 and S are grounded or connected to earth, the counterelectrode between the insulating support and the collecting element isconnected to a potential of the desired level. The counter electrode isin the form of a lattice or grid, it may also be in the form of singlewires, e.g. laid in loop form, or in the form of stretched wires, whichmay, e.g. surround one another concentrically. In any case it must bepermeable, i.e., it must permit passage of the particles 6 in powder orgranular form which are lying on the side of the insulating support 1facing the collecting element 2. First, the coating material 6 is finelydis persed onto a support 1 lying opposite or facing the collectingelement in the embodiment according to FIG. I it is a sheet ofinsulating material in such a manner that it lies on this in a uniform,or almost even or uniform, loose layer. After this step, the coatingmaterial on the insulating support is vibrated or shaken loose of thissupport. An electrostatic pulsating field is generated between theinsulating support and the collecting element and the shaking orvibrating movement is executed in such a manner that the coatingmaterial becomes immersed in the electrostatic field. The loosenedcoating material is then accelerated by the electromagnetic field andhurled and sprayed against the collecting element. The single stepscould possibly be carried out in series, like in a mass production, e.g.by making pass consecutive plate-like insulating supports or a conveyorbelt acting as the insulating support first through a station where thecoating material is brought thereupon or applied thereonto and then bysubjecting it to the effect of the electrostatic field at a subsequentstation. In the arrangement shown in FIG. 1, the shaking or vibratingloose of the coating material is carried out by electrical means. Theparticles sprayed or hurled onto the collecting element 2 as indicatedby the arrows 14 are held on the collecting element in that the latteris assigned a potential which differs from the potential of one of theelectrodes of the electrostatic field, e.g. an electrode 5 which isgrounded or connected to earth may be provided at the side of thecollecting element facing away from the counter electrode 4, whereas thecounter electrode 4 is connected to the respective potential. Finally,the coating, if it consists of pulverized or granular particles ofsynthetic material will be bonded to the collecting element by stoving,baking or burning in. In other cases, when the coating materialconsists, for example, of sand, the side of the collecting elementfacing the insulating support may be coated with adhesive in order toimprove and strengthen adhesion. The adhesive effect may eventually alsobe increased by shooting" the particles on a sheet or synthetic materialwhich has been made soft and sticky on the side facing the insulatingsupport. To achieve this end, the collecting element may be warmed orheated. Finally, there are also applications, e.g. when the coatingmaterial is of polyvinylchloride, in which the coating applied forms asingle cohesive layer after baking, so that this layer may be strippedoff or detached from the collecting element.

In the arrangement shown in FIG. 2, between the insulating support towhich one electrode 17 is assigned on the side facing away from thecollecting element, and the collecting element 16 there is provided onthe one hand a counter electrode 18 and, on the other hand an auxiliaryelectrode 19 associated or connected with a high dc. voltage orpotential, e.g. again consisting of single stretched wires or in theform of a lattice or grid. The counter electrode is insulated. It mayconsist, for example, of wires surrounded by a layer of insulatingmaterial, e.g. synthetic material, it may, of course remain uninsulated,however. The auxiliary electrode and the counter electrode may have thesame potential, in which case they may e.g. be connected to one anotherby insulated connecting electrodes, but they may also have differentpotentials. In the arrangement shown in FIG. 2, the collecting element16 is itself the electrode.

Of course, the electrodes 3 or 5 of the arrangement shown in FIG. 1, and17 and 16 of the arrangement shown in FIG. 2 may be connected to a solepotential, and the counter electrodes 4 (FIG. I) or 18 and eventually 19(FIG. 2) may be grounded or connected to earth. Of course, all thecounter electrodes between the insulating support and the collectingelement two or more such electrodes may be provided may be connected tothe same potential. It may also be that some of the counter electrodesare of a different potential. It is also possible e.g., to ground theelectrode associated to the collecting element, to connect the electrodebetween the insulating support and the collecting element to a dcvoltage, and to connect the electrode on the side of the insulatingsupport facing away from the collecting element to an a.c. voltage. Whenthere are several counter electrodes, the counter electrode nearest tothe insulating support and the electrode facing the collecting elementmay be grounded, whereas the electrode facing away from the insulatingsupport may be connected e.g. to a dc. voltage of up to 30 KV and more(e.g. 100 KV) and the electrode associated to the insulating support maybe connected to an a.c. voltage of e.g. 6 l6 KV.

For the even distribution of the pulverized or granu lar particles onthe layer of insulating material, a sheet or layer 20 of open-poredsynthetic foam material is provided above the insulating support 22which is held in a frame 21 or mounted on some other form of support andwhich moves to and fro in the manner of the shaking or vibratingmovement of the machine frame in a direction indicated by the arrow 23which is parallel or almost parallel or eventually also as indicated bythe arrow 24 obliquely or at an angle to the surface of the support 22carrying the particles 25 of the coating material. This plate 20 ofsynthetic foamed material is connected to, e.g. an electric drive motornot shown here, which imparts the vibrations when the plate is operated,but may, however, be arrested during the remnant time. Instead of foamedmaterial, another material, e.g. ceramic material or the like may beused. This device may also serve for cleaning contaminated or pollatedcoating material.

The device for performing the method according to the invention shown inFIG. 4 has an insulating support 31 of synthetic material which has theform e.g. of a potor basinor bowl-like container open at the end facingthe object to be coated and closed at the other end by a closing wall,for example, a bottom wall. This container 31 is thus open in thedirection facing the object to be coated 32 and closed at the other endby the bottom wall 33. It also has side walls 34 so arranged as topermit immersion of the object to be coated more or less deeply into thepot. The electrode 35 is mounted on the side of the bottom wall facingaway from the object to be coated, and on the other side of the bottomwall there is at least one counter electrode 36.

The rims 35a of the electrode 35 and 36a of the counter electrode 36 areturned upward slightly so that they face the lowest part 340 of the sidewalls of the container and cover this part towards the outside or theinside. In this way any desired orientation of the particles of thecoating material may be obtained. Furthermore, it is thus possible toprevent the powder (coating material) from being deposited on the rimsand from drifting towards the centre with round or circular containers.

With the arrangement shown in FIG. 5, the insulating layers 38, 39 areof synthetic material and are stairshaped or stepped. However, theselayers may also be given the form of an L or similar shape, whereby itis essential that there are at least two surfaces running transverselyor approximatively rectangularly to one another, of which the onesurface in the drawing of the embodiment, respectively the surfaces 380and 39a serves as receiving portion to receive the coating materialwhich is fed in as indicated by the arrow 40. The insulating supportextends conveniently along the entire length of the object to be coated.It may, however, correspond to only a section of this length so thatsome provision will have to be made for the movement of the insulatinglayer and the collecting element in relation to one another inlongitudinal direction, e.g. in that the object to be coated is movedpast the insulating layer. On one side of the receiving portion whichreceives the coating material, there is an electrode 41 or 42, and onthe other side there is the counter electrode 43 or 44, whereby the rims41a, 42a, 43a, 44a of the electrode and the counter electrode are turnedupward on the side facing away from the object to be coated 40c suchthat they cover the lowermost edge of the rear surface 38b or 39b (asviewed from the object). This again has the object of permitting theorientation of the movement of the powder particles. On the side facingthe object to be coated, the rims of the electrode and the counterelectrode are shorter than the surface 38a of the insulating supportbetween them so as to stand back by the amount 40d. The coating materialfalling on the receiving surface as indicated by the arrow 40, is firstthrown up as indicated by the arrow 40a and shaken or vibrated loosefrom the surface and then as a consequence of the above-describedarrangement of the electrode and counter electrode, it is sprayed andhurled as indicated by the arrows 40b in the direction of the object tobe coated 40c. Several stepped or stairshaped, L-shaped or similarlyshaped insulating supports may be arranged over one another or facingone another and may be parallel or at an angle, e.g. in zigzagconfiguration, to one another. a

The device may be provided with means for generating an air cushion,which in the case of extremely great distances serves to aid themovement of the particles of 5 coating material in direction towards thesurface to be coated. An improvement in the same direction may beobtained if, in accordance with an embodiment of the invention notdescribed further here, a feed container is provided at some greaterdistance or at a greater height above the insulating support, wherebythe coating material is conveyed to the receiving surface e.g. by freefall.

The flow of coating material in the direction of the surface to becoated may be further intensified in that the ends of the wires of thegrid-like counter electrodes pointing towards the object to be coated,are free on the side facing the said object and protrude by a specifiedamount beyond the rest of the counter electrode. In this manner, theparticles of the coating material will be hurled with greatest intensityand concentration on the surface to be coated. As shown in FIG. 6, theinsulation support may also be given the shape of a shallow bowl basin45, whose side walls 45a, 46a slope slightly upwards and outwards, itsouter edges may, but do not have to, be bent downwards as shown by 45b,46b. The coating material falls from above as indicated by the arrow 47onto the bowl or basin, but may also be supplied from below, e.g. via ahouse 48 or a pipe. in this case a sloping surface 49 may be providedbeneath the insulating support to catch falling coating material whichthen flows as indicated by the arrow 50 in the towards direction of thecollecting surface or outlet opening 51. An arrangement of this type issuitable for coating the inner surface of hollow bodies 52.

FIG. 7 shows a modification of the invention in which the insulatingsupport 65 may be given the form of an elongated body which may becurved as shown in the drawing or prismatic or cylindrical, with anopening which may be either circular or rectangular. The coatingmaterial is fed in at the end 66 and emerges at the other end. The sidewalls of the body 65 are covered on the outer side by the electrode 67and on the inner side by the counter electrode 68, either partially orentirely, whereby they conveniently leave uncovered the extreme end ofthe insulating support in the area of the outlet opening. in this way ashort circuit between counter electrode and electrode becomesimpossible. In the modification shown in FIG. 8, the outlet opening 80of the insulating layer has an L-shaped section. In the modificationshown in FIG. 9, the outlet opening 81 of the insulating layer has aT-shaped section.

An arrangement is also possible in which, for example, an insulatingsupport runs obliquely or at an angle to the direction of feed, formingan angle with it which may be 5 or Instead of the layer itself runningat an angle in this manner, a sloping catching surface may be providedbeneath the insulating support which serves to remove coating materialin excess. Such catching surface may consist of several sections at anangle to one another, which form a kind of funnel which may be eithersymmetrical or nonsymmetrical and which is characterized in that as fora collecting surface in one piece the sections lead to a lowest pointassociated to an outlet for the recovery of coating material in excesswhich leads to a removing channel or cavity or tunnel from which thematerial may be recycled by conventional means, eg pneumatically, with aworm or the like. Behind the outlet opening there may be convenientlyprovided a filter, serving to clean the fallen material, which mayconsist of a layer of openpored foamy plastic or sponge rubber or thelike and which may be vibrated together with the collecting surface orsurfaces.

The coating material may be fed manually or mechanically from above,from below or from the side. In one embodiment not shown in the drawing,the coating material is fed via a feed channel which may be vibrated bymeans of so-called vibrators or the like, said channel being mountedabove the insulating support and attached at one end to a collectingfunnel. This channel has numerous slits or holes which may be evenly oruniformly distributed along its entire length. Due to the vibration, thecoating material coming from the feed funnel drifts slowly through thechannel, which e.g., may be sloping, and can drop down on the layer ofinsulating material.

What we claim is:

l. A device for coating objects with small particles on a collectingelement which comprises an insulating support means for such particles,means to agitate particles on the support, a first electrode member onone side of said supportmeans, a counter-electrode member on the otherside of the support means from said first electrode member, saidcounter-electrode member having spaces therethrough, said agitatingmeans comprising means to create a first alternating currentelectrostatic field between the first electrode member and thecounter-electrode member to displace particles from said support means,and means to create a second electrostatic field between thecounter-electrode member and a collecting element on the opposite sideof the counter-electrode member from the support means, said last meanscomprising means to charge said counterelectrode member and saidcollecting element with different potentials, whereby to depositparticles from said support means on such collecting element.

2. In a device as claimed in claim 1, said second field creating meanscomprising a second electrode member on the other side of thecounter-electrode member from the first electrode member.

3. In a device as claimed in claim 1, one of said members beinggrounded.

4. The device as claimed in claim 1, the insulating support means havingthe form of a basin-like body open at the end facing the collectingelement and closed at the other end and the first electrode member beinglocated at the side of the bottom wall facing away from the collectingelement to be coated, and at least one said counter-electrode memberbeing located at the side of the wall facing the collecting element tobe coated, the rims of the electrode member and the counter-electrodemember being turned slightly upwards, the wall of the basin-like bodyextending further upward than the rims of the electrode member and thecounter-electrode member.

5. The device as claimed in claim 1, in which the insulating supportmeans comprises a layer of insulating material and has at least twotransverse surfaces at different levels from each other, of which oneserves to hold the coating material, and the insulating support meansextending along the entire length of the collect ing member on one sideof the insulating support means, the rims of the electrode member andthe counter-electrode member on the side facing away from the collectingelement being turned upward so that they cover the lower edge of therear surface as viewed from the collecting element.

6. The device as claimed in claim 5, in which the insulating supportmeans comprises several stepped stairshaped insulating supports over oneanother in which the surface which hold the coating material, whenviewed along the length of the collecting element slope to such anextent that viewed, along the length of the supporting means, thebeginning of one is on the same plane or at the same height as the endof the following one.

7. The device as claimed in claim 6, in which there is provided a feedcontainer associated with the insulating support means arranged at agreater height above it, from which the coating material is fed onto thesurface holding it by free fall.

8. The device as claimed in claim 1, in that the insulating supportmeans has the form of a shallow bowl with sides sloping slightly upwardsand outwards, and

means for feeding the coating material is fed into it.

9. The device as claimed in claim 8, wherein the insu lating supportmeans has a wall running at a slight angle to the direction of feed,said wall comprising several sections at an angle to one another in sucha manner that the sections of the surface to a lowermost point wherethere is an outlet for the recovery of coating ma terial in excess andleading to a removing channel from which the material may be recycled10. The device as claimed in claim 1, in which the insulating supportmeans has the shape of an elongated prismatic body at one end of whichthe coating material is fed and whose opening serves to expel thecoating material, the side wall of the body being at least partiallycovered in the outside by the first electrode member and on the insideby the counter-electrode memher, said members leaving the extreme end ofthe insulating support means uncovered in the area of the outletopening.

1. A device for coating objects with small particles on a collectingelement which comprises an insulating support means for such particles,means to agitate particles on the support, a first electrode member onone side of said support means, a counter-electrode member on the otherside of the support means from said first electrode member, saidcounter-electrode member having spaces therethrough, said agitatingmeans comprising means to create a first alternating currentelectrostatic field between the first electrode member and thecounter-electrode member to displace particles from said support means,and means to create a second electrostatic field between thecounter-electrode member and a collecting element on the opposite sideof the counterelectrode member from the support means, said last meanscomprising means to charge said counter-electrode member and saidcollecting element with different potentials, whereby to depositparticles from said support means on such collecting element.
 2. In adevice as claimed in claim 1, said second field creating meanscomprising a second electrode member on the other side of thecounter-electrode member from the first electrode member.
 3. In a deviceas claimed in claim 1, one of said members being grounded.
 4. The deviceas claimed in claim 1, the insulating support means having the form of abasin-like body open at the end facing the collecting element and closedat the other end and the first electrode member being located at theside of the bottom wall facing away from the collecting element to becoated, and at least one said counter-electrode member being located atthe side of the wall facing the collecting element to be coated, therims of the electrode member and the counter-electrode member beingturned slightly upwards, the wall of the basin-like body extendingfurther upward than the rims of the electrode member and thecounter-electrode member.
 5. The device as claimed in claim 1, in whichthe insulating support means comprises a layer of insulating materialand has at least two transverse surfaces at different levels from eachother, of which one serves to hold the coating material, and theinsulating support means extending along the entire length of thecollecting member on one side of the insulating support means, the rimsof the electrode member and the counter-electrode member on the sidefacing away from the collecting element being turned upward so that theycover the lower edge of the rear surface as viewed from the collectingelement.
 6. The device as claimed in claim 5, in which the insulatingsupport means comprises several stepped stair-shaped insulating supportsover one another in which the surface which hold the coating material,when viewed along the length of the collecting element slope to such anextent that viewed, along the length of the supporting means, thebeginning of one is on the same plane or at the same height as the endof the following one.
 7. The device as claimed in claim 6, in whichthere is provided a feed container associated with the insulatingsupport means arranged at a greater height above it, from which thecoating material is fed onto the surface holding it by free fall.
 8. Thedevice as claimed in claim 1, in that the insulating support means hasthe form of a shallow bowl with sides sloping slightly upwards andoutwards, and means for feeding the coating material is fed into it. 9.The device as claimed in claim 8, wherein the insulating support meanshas a wall running at a slight angle to the direction of feed, said wallcomprising several sections at an angle to one another in such a mannerthat the sections of the surface to a lowermost point where there is anoutlet for the recovery of coating material in excess and leading to aremoving channel from which the material may be recycled.
 10. The deviceas claimed in claim 1, in which the insulating support means has theshape of an elongated prismatic body at one end of which the coatingmaterial is fed and whose opening serves to expel the coating material,the side wall of the body being at least partially covered in theoutside by the first electrode member and on the inside by thecounter-electrode member, said members leaving the extreme end of theinsulating support means uncovered in the area of the outlet opening.